Thanks for writing your query.
It will be helpful if you mention the name of any medicine you are taking for your sore throat
After reading your post, I would suggest that you should go for a Throat swab culture to know the infective organism and the appropriate antibiotic for that organism.
Some antibiotics disturb the normal useful bacterial flora of the intestine resulting in loose motion
will help in regaining the lost flora and treat antibiotic induce loose motions.
If the problem persists, get yourself clinically examined and investigated.
I hope this is helpful to you.